1. Field of the Invention
The present invention relates to a plasma processing apparatus and used for etching, ashing, chemical vapor deposition (CVD), etc. in the manufacturing, etc. of large-scale integrated circuits (LSIs) and liquid crystal display panels (LCDs).
2. Description of the Related Art
Processes based on plasma of reactive gases are adopted widely in the manufacturing of LSIs, LCDs, etc. Particularly, the dry etching technique using plasma is an indispensable fundamental technique for the manufacturing processes of LSIs, LCDs, etc.
Recently, plasma generation apparatuses based on the microwave are used for plasma processings because of the ease of high-density plasma generation as compared with the conventional scheme of using high frequencies around 13.56 MHz.
However, microwave-based plasma generation apparatuses generally involve the problem of generating plasma uniformly over a wide area. The present inventors have attempted to resolve the above-mentioned problem and have proposed a plasma processing apparatus having a dielectric plate in Japanese patent publication JP-A-Sho-62-5600.
FIG. 1 is a vertical cross-sectional view of a conventional plasma processing apparatus having a dielectric plate. The apparatus has a reaction chamber 11 (reaction room 12), in which a sample stage 15 is disposed. The top of the reaction room 12 is covered with a microwave window 14 which confronts the sample stage 15, and the reaction room 12 is sealed airtight. A dielectric plate 32 is disposed over the microwave window 14 with a hollow section 31 interposed these between. The microwave window 14 is a flat plate made of quartz glass (SiO.sub.2), alumina (Al.sub.2 O.sub.3) and so on.
A microwave generator 35 generates a microwave, which is supplied to the dielectric plate 32 through a waveguide 34. The microwave propagated in the dielectric plate 32 produces an electric field under the plate 32, and the electric field, exerted in the reaction room 12 through the microwave window 14, causes gas, which is fed to the reaction room 12 through a gas inlet hole 25, to excite and generate plasma. By this plasma, the surface of a sample S undergoes a plasma process such as etching.
This apparatus is also advantageous to generate uniform plasma over a wide area by having a large microwave window 14 and a large dielectric plate 32.
However, the conventional plasma processing apparatus using a dielectric plate is designed to generate plasma over a wide area relative to the sample in order to achieve a uniform plasma processing rate over the entire sample surface. As a result, the apparatus has the problem of a lower plasma density and thus, a lower plasma processing rate, and the problem of the failure of etching off a fine hole pattern down to the bottom.
The present invention is intended to resolve the foregoing problems, and its object is to provide a plasma processing apparatus which is capable of increasing the plasma density in the sample exposure area to thereby improve the plasma processing rate, and which is also capable of improving the etch-through performance for fine hole patterns.